Inorganic chemistry : theoretical and practical with an introduction to the principles of chemical analysis an elementary text-book

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INORGANIC CHEMISTRY

THEORETICAL & PRACTICAL

WITH AN INTRODUCTION TO THE PRINCIPLES OF CHEMICAL ANALYSIS INORGANIC AND ORGANIC

AA ELEMENTARY TEXT- BOOK

WILLIAM JAGO, F.C.S., F.I.C.

HEAD SCIENCE MASTER OF THE BRIGHTON SCHOOL OF SCIENCE AND ART

THIRTEENTH EDITION

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PRE FAC E

TO

THE NINTH EDITIO X.

It was with some hesitation that I undertook the task of writing the first edition of this book, feeling as I did that a number of chemical works of a high character were already in existence. From the point of view of a teacher brought continuously into contact with large classes being taught under the regulations of the Science and Art Department, and also with other students preparing for various examinations, I felt there was still something wanting in the way of a text-book specially arranged to meet these requirements, and hence the first appearance of the present book. The work, when published, received a welcome both from teachers and the press far exceeding what I had ventured to hope or expect. Six years have now elapsed since that first edition was written ; during that time considerable changes have been made in the chemical syllabus issued by the Science and Art Department. Among the most important of these was the publication in 18X5 of an ‘Outline of

Vl Preface.

Experiments suitable for illustrating Elementary Instruction in Chemistry,’ prepared by Sir H. E. Roscoc and Dr. W. J. Russell. This Outline of Experiments was commenced with the significant remark that

the following notes have been prepared as some guide to the teachers as to the general character of the course of instruction expected in the elementary stage. It includes instruction that should on no account be omitted, but must be considered rather as suggestive than exhaustive.

As a consequence of these alterations it became absolutely necessary that a text-book for the use of students of classes connected with the Science and Art Department should include the whole of the subject-matter indicated in this recent addition to the syllabus. In order to attain this end I have carefully re-written the whole book, and, disturbing the original plan as little as possible, have incorporated with it any additional matter required to make it fully meet the requirements of both students and teachers. A number of additional questions have been added to those given at the end of the book. In particular, greater attention is given to the exercises on chemical calculations : a number of typical examples are selected and worked out in detail, in order to illustrate the principles im olved. In this edition the paragraphs are numbered and hav e side headings. The more important statements and definitions are printed in bolder tvpc. These modifications will, I hope, be of assistance to the student.

Preface

Vll

A number of both students and teachers have pointed out to me that they have been using this work in preparing for the matriculation examination of the London University, but have been inconvenienced by its not covering the whole of the syllabus of that examination. In the present edition chapters have been added in order to supply this want ; accordingly the book in its present form embraces the whole subject-matter necessary. At the discretion of their teachers, Science and Art Department students may omit this additional matter, which is contained in the following paragraphs: 108-110, 116-129, and 195 to end. I strongly recommend them, however, to read at least the intermediate paragraphs referred to, as by so doing they will gain a more complete elementary knowledge.

In conclusion I wish to tender my thanks to both reviewers and teachers for the kindness with which this book has been received in the past, and for the suggestions as to increasing its usefulness with which they have favoured me. Many of these have been of considerable value, and so far as practicable have been adopted.

WILLIAM JAGO.

Phosphorus and Silicon

3”

INDEX b

TEXT-BOOK

OK

INORGANIC CHEMISTRY.

Chapter I. Introductory

I. Definition of Chemistry.— Phenomena are continually taking place around us to which we give the name of ‘ chemical actions.’ For instance, a piece of bright iron speedily rusts when exposed to damp air ; milk, as a result of exposure to the atmosphere, turns sour and acquires properties strikingly different from those possessed by that fluid when first obtained from the cow ; coal, wood, and a host of other bodies, which are classed together as combustibles, burn on a light being applied to them, leaving in most cases no visible residue beyond a small quantity ot ash. It is the function of the chemist to investigate these changes, and ascertain, as far as he can, the nature of the substances participating in the action and its causes. Chemistry, then, may be defined as ‘that scienco which treats of the composition of matter, of changes produced therein by certain natural forces, and of the action and reaction of different kinds of matter on each other.’

Text-Book of Inorganic Chemistry.

The word ‘matter,’ which is here used, is employed scientifically to signify anything which has weight, i.e. which is acted on by gravitation. Stones, earth, water, and even gases, are matter.

2. Experimental Study necessary.— There is no science which is not better studied by the aid of experiments than without ; but while this is simply an additional advantage in some other sciences, it is absolutely necessary in the case of that of chemistry.

This book is intended, not only as a text-book for theoretical study, but also as a guide to practical work in the laboratory ; the experiments are, for this reason, not referred to descriptively, but, instead, practical directions are given for their performance ; except in some few instances, where they are of a nature more suited for the lecture table than to be tried individually by each student of a class.

It cannot be impressed too strongly at the outset that chemistry cannot be thoroughly and efficiently mastered without this work being actually performed by the student, and not merely seen performed. His own mind and hands should put the experimental question to nature, and his own powers of observation must learn to accurately interpret her answer.

The student will find at the close of this chapter some directions and hints for his use on first commencing work in the laboratory. He will, in all probability, have had the advantage of seeing the experiments performed by the teacher during the lecture preceding the laboratory lesson.

3. Characteristics of Chemical Action.— It is first necessary to carefully distinguish between what are merely alterations in the physical properties of matter and what are real chemical changes. This is best seen -by an actual experiment.

Experiment r. — Heat a piece of platinum wire in the flame of a Bunsen gas lamp ; it immediately becomes white hot ; rc-

Characteristics of Chemical Actio n. 3

move it, and, as the wire cools, it once more regains its original brightness. It is not in the least altered, not even tarnished.

Next heat in the same way a piece of bright iron wire: this is tarnished, but otherwise will have undergone no great change.

Next place a piece of magnesium wire or ribbon in the flame : it burns with a dazzling white light, depositing a white, easily powdered body, composed of oxygen and magnesium, and known as magnesia.

In the first case the change produced is merely physical, and although the hot wire possesses properties which are absent in the cold, yet on the wire losing its heat it again regains its previous characters. With the iron wire a slight permanent change is produced on the surface : this is of a chemical character, but the main portion of the wire is unaltered. In the third instance a vigorous chemical change has occurred ; the magnesium, as such, has entirely disappeared and a new body takes its place. The student hereby learns that chemical changes are distinguished from those of a merely physical character by moro or less striking permanent alterations in the appearance and properties of the substances involved therein. The following are additional examples of changes produced by chemical action.

Matter occurs in three states, solid, liquid, and gaseous ; chemical action is very frequently accompanied by a change from one of these to another.

Experiment 2. — Place in a test-tube some dilute sulphuric acid, in another about the same quantity of solution of calcium chloride ; notice that each is a transparent, colourless liquid. Add the one to the other ; in a few seconds the whole has become a solid mass, and the test-tube may be inverted with only a few drops of the liquid running out. In this case a new body has been produced, called calcium sulphate, which combines with a portion of the water present to form a solid.

Not only may liquids be converted into solids, but

a 2 solids in very many chemical changes are transformed into gases.

Experiment 3. — .Light a piece of candle : it gets less by the act of burning, and ultimately would entirely disappear — the solid fat, composed of hydrogen and carbon, is being changed into gaseous compounds. Hold a cold surface, as the outside of a porcelain dish filled with water, in the flame : it gets blackened, owing to the separation of carbon as soot or lampblack ; and also becomes wet, through the deposition of water produced by the combination of hydrogen with the oxygen of the atmosphere.

Pour into a glass gas jar, or colourless glass bottle, of about a pint capacity, a layer of half an inch of clear lime-water ; shake up the jar, the lime-water remains clear. Next take a small piece of candle and fix it in a deflagrating spoon ; light it and place in the glass jar ; it soon goes out ; again shake the jar — the lime-water now becomes turbid through the formation of a compound of lime and the carbon dioxide produced by the oxidation of the carbon of the candle.

The small wax tapers used for lighting Christmas trees, &c., are very suitable for these experiments.

Although, in burning, the candle disappears, the bodies of which it is composed can thus be traced ; for the disappearance of the candle is accompanied by the production of water, and also an invisible gas, which evidently differs from ordinary air, because it turns the lime-water milky, while, as the student will have seen, air is unable to produce this change.

4. Indestructibility of Matter— By experiments similar in principle to that just described, but of a more exact character, in which quantity is estimated, it is found that the whole of the matter present before the combustion still exists after. Matter is indestructible ; and consequently the same weight of material remains after any and every chemical change as there was before its commencement.

Indestructibility of Matter.

Experiment 4.— Take a glass chimney, such as is used for Argand lamps ; fit a cork to each end ; bore several holes in the lower cork, one being in the centre and of a size to fit a small taper, which must be inserted in it. Thrust a piece of wire gauze about two-thirds of the way up the chimney, so as to form a tight plug ; fill this upper chamber with fragments of caustic

Fig. 1.

soda ; bore a hole through the centre of the top cork and pass a piece of small glass tubing through. When complete, weigh the whole apparatus carefully ; next place it in a retort-stand and, by means of india-rubber tubing, connect with the shoit tube passing through the cork of a two-gallon can, filled with water, having a stop-cock at the bottom. Open this cock, and, as the water runs out, it causes a current of air through the

Text- Book of Inorganic Chemistry.

apparatus. Take out the taper, light, and quickly replace it ; allow it to burn for three or four minutes, then turn off the cock

the taper goes out ; disconnect the tubing from the top cork and again weigh ; the weight has increased, owing to oxygen laving been taken up from the atmosphere by the burning taper ; it has combined with its constituents to form water and carbon dioxide respectively. These compounds are both aDsoroed and retained by the caustic soda. The apparatus is shown in 1 ig. i. The student, working in a laboratory, will probably find these pieces of apparatus already prepared ready for use. As there is not likely to be a sufficient number for each student to tiy the experiment at the same time, it must be taken in turns.

So far from the burning of a candle being accompanied by any loss of its constituents, the weight of the resultant products is greater than that of the candle itself, because they contain in addition the oxygen removed from the atmosphere. Matter being indestructible, it follows that when chemical combination occurs between substances, the weight of the products is exactly the same as that of the bodies previous to chemical action. Proof of this statement will be afforded by experiments described in later chapters.

5. Distinction between Mechanical Mixture and Chemical Union. — The student who has carefully performed the preceding experiments will scarcely need to be told that chemical combination is widely different from mere mixture. In the latter case the resultant body is a mean in appearance, specific gravity, dire., between its constituents : they still each possess their individual properties, and the separate particles may be seen with sufficient magnifying power.

Experiment 5. — Take some finely divided copper; notice its colour; mix intimately with powdered sulphur; the mixture has a tint intermediate to that of the substances when separate. Place some of the mixed powder in an evaporating basin, and

Mixture and Combination.

wash with a gentle stream of water ; notice that the sulphur is carried away, and that the heavier copper remains behind. This and several other methods may dc employed to effect their mechanical separation, which is easily done, as there is no union between them. Next, place some of the mixture in a dry test-tube, and heat ; observe that the sulphur first melts, and that shortly after the whole mass glows brightly. When cool, examine the resulting substance ; it is of a bluish-black colour, brittle, and one of its ingredients can no longer be separated from the other by the action of water or mere solvents. A new body has been formed by the union of the sulphur and copper, known as copper sulphide.

Not only does chemical combination produce bodies different from a mixture of the constituents, but it is also accompanied by an evolution of heat.

In addition to the proofs of this statement afforded ' by previous experiments, the following shows the production of heat by chemical combination in a striking manner.

Experiment 6. — Place a few fragments of recently burned quicklime in a saucer or evaporating basin, and pour in sufficient cold water to just moisten the lime. In a short time the lime becomes very hot, and the water as such entirely disappears. £

The heat in this experiment is due to chemical combination between the water and the quicklime.

The difference in appearance of bodies as a result of chemical combination and the production of heat are two of the principal characteristics by which a chemical union between substances is detected.

6. Element, Compound, Mixture.— It is well at this early stage of study to have accurate and concise ideas of the meaning attached to the terms, element, &c. Definitions are therefore appended : —

An ELEMENT is a substance which has never been separated into two or more dissimilar substances.

Text-Book of Inorganic Chemistry.

A COMPOUND is a body produced by the union of two or more elements in definite proportions, and consequently is a substance which can be separated into two or more dissimilar bodies. Compounds differ in ‘appearance and characteristics from their constituent elements.

The term MIXTURE is applied to a substance produced by the mere blending of two or moro bodies, elements or compounds, in any proportion without union. Each component of a mixture still retains its own properties, and separation may be effected by mechanical means.

7. Synthesis and Analysis —In the experiments hitherto performed the operations have been of the kind known as ‘synthesis,’ that is, the putting together of elements and building up new compounds. Another most important mode of chemical investigation is ‘analysis, which consists of decomposing bodies, resolving them into their elements or simpler compounds.

Experiment 7.— Place some red mercuric oxide, about as much as could be held on a threepenny piece, in a dry test-tube ; close the mouth loosely with the thumb and apply heat. Notice that the colour changes from red to black, the oxide gradually disappears, and minute globules of metallic mercury condense on the upper part of the tube. Next light a splinter of wood, a match will do very well ; when well lighted blow out the flame, and introduce it while still glowing into the tube ; it immediately again bursts into flame, thus showing the presence of the gas called oxygen.

In this experiment a compound has been separated into its two elements ) or in other words its analysis has been effected.

8. Relation of Chemical Action to Force.— It

has been already stated that when chemical combination occurs heat is generated ; in order to effect the change

Chemical Action and Force.

described in the last experiment heat has been used and has disappeared as such, being stored up in the the form of the available or potential energy of chemical attraction or affinity. If the mercury and oxygen are again caused to combine the act of reunion will once more set free the exact amount of heat that was necessary to e ic their decomposition. Many instances are known m which bodies that evolve a certain amount of heat on uniting may be again decomposed by being subjected to a more intense heat. In all such cases the quantity of heat evolved during chemical combination is oxactly oqual to that requisite to effect the decomposition of the

resultant body. . , ,

Further, by proper appliances the chemical action ot

elements entering into combination may be caused to produce electricity ; and electricity in its-turn is competent to dissociate the elements of compound bodies. 1 here is in this case also a definite .relation between the amount of chemical action and the quantity of electricity produced.

Force is defined as that which is capable of setting matter in motion; consequently chemical combination must be ranked among the forcos ; lor such chemical actions, of which the combustion of coal is a typical example, generate heat, and thus indirectly, as in t le steam-engine, constitute our most valuable means of setting matter in motion and overcoming resistances generally.

9. Relation between Gravitation, Cohesion, and Chemical Attraction.— Matter is maintained in its normal state through the Universe by the action of three most important forces— gravitation, cohesion, and chemical attraction. The first of these acts through all space, and exerts an attraction between all matter. Cohesion acts only across non-appreciable distances, holding together the particles of solids, and also, though to a much less extent, those of liquids.

Text-Book of Inorganic Chemistry.

Experiment 8. — Attach a clean glass plate about 4 or 5 inches in diameter to pieces of wire in the same way as a scale pan is suspended from the end of the arm ; place it in a basin of water, so that the glass plate just floats on the surface ; notice the pull necessary to tear it away from the water and overcome the cohesion existing between its particles. The amount of this cohesion may be approximately measured by suspending the glass plate from the arm of a balance, and counterpoising it in air; the plate is then floated on water and weights added to the pan until the two are separated.

By means of heat this force may be often overcome ; thus solid ice may be converted into water ; a further increase of temperature destroys the remaining cohesion and produces steam, which, in common with all other gases, is devoid of any cohesion between the particles. But, whether as ice, water, or steam, the substance is the same in chemical properties. By application of a more intense heat, however, the steam is decomposed into oxygen and hydrogen. Heat, therefore, not only destroys cohesion, but when sufficiently intense overcomes the force of chemical attraction which holds the elementary atoms of all compound substances together.

Summary.

Every-day instances of chemical action. Definition of chemistry. Experimental study is essential. Chemical action is accompanied by change of appearance, &c. Liquids into solids. Solids into gases.

Matter is indestructible ; in no chemical change is it lost.

Chemical combination is essentially different from mere mixture ; not only accompanied by change of appearance, but also by evolution of heat.

‘ Element,’ &c., defined.

Two most important types of chemical action, synthesis and analysis.

Heat is capable of effecting the decomposition or analysis of compounds. The quantity necessary is reproduced when the elements recombine.

Summary and Laboratory Hints. 1 1

Chemical action may generate other forces, as heat and electricity ; it is itself, therefore, a FORCE.

Chemical affinity holds together the elementary particles in compound bodies. Heat overcomes it, and dissociates them.

Laboratory Hints.

In the laboratory the student will either have to provide for himself, or be supplied with, a set of apparatus sufficient for the performance of the common experiments. Such a set should include —

Bunsen’s burner and iron rose, with 2 feet of india-rubber tubing.

Retort-stand and spring clamp.

Two pieces of iron wire gauze 5 inches square.

Three flasks, respectively of 4, 8, and 16 oz. capacity.

Six test-tubes, 6 inches by ^ inch diameter.

Test-tube brush.

Thistle funnel 18 inches long.

Glass funnel 2 inches diameter.

Dozen assorted corks.

Brass crucible tongs.

Small evaporating basin, about 2i inches diameter.

Small beaker, 4k oz. capacity.

Two books of litmus paper, red and blue.

£ lb. small glass tubing.

Two feet small india-rubber tubing.

Four gas bottles.

Four ground glass plates.

Messrs. Orme & Co., of 65 Barbican, London, E.C., supply the author with these sets of apparatus in boxes at 17s. They keep the sets in stock, and the apparatus is always reliable.

The following apparatus is generally supplied for common use : —

Earthenware pneumatic troughs and beehive shelves. Deflagrating spoons and caps.

Deflagrating jars, open at top and bottom.

Retorts of various sizes.

Cork borers.

Pestles and mortars.

Aspirator, balance, weights, &c.

Text-Book of Inorganic Chemistry.

The more expensive pieces of apparatus must be obtained, when required, by application to the teacher.

The student should, in the first place, make himself familiar with the names and uses of his apparatus. Let him next carefully and thoroughly clean the glass and porcelain vessels. The chemicals required will be found as a rule in bottles and jars, so placed as to be readily accessible to the whole of the students. They should under no circumstances be removed from their places ; the quantity required should be taken in a flask or test-tube, and the bottle immediately restored to its place. A strict adherence to this rule prevents the loss of a great amount of time which would otherwise be spent in searching over the laboratory for bottles, &c.

In getting the chemicals for an experiment, be sure the right ones are taken ; see that concentrated acids are not used where dilute should be employed ; never use pure substances when the commercial will answer the purpose ; do not let the stoppers of bottles lie about or get mixed. Take no more of the substance than you require, and if you happen to have an excess do not return it to the bottle without express permission ; much confusion has been caused by chemicals being replaced in the wrong bottles.

When directions are given that substances are to be mixed, , solid bodies are to be first powdered, and then stirred together until the mixture is as uniform as possible.

Heat is applied to tubes, &c., by means of the Bunsen burner ; before lighting it see that the holes at the bottom are open ; the flame should be non-luminous ; if smoky, it is a sign that the gas is burning at the lower end of the tube of the burner ; it must be turned out and re-lighted. This catching fire at the bottom is the result of an excess of air entering ; the remedy is to turn on more gas, or partly close the air-holes by turning the ring of the burner over them. In heating test-tubes, the heat must be applied gently at first, with a constant motion of the tube, or, if the tube be fixed, of the burner.

If heating a liquid, never let the flame play on the part of the tube above its surface. When a solid is being heated, if any moisture happen to be present, it condenses in the upper and coo'er parts of the tube ; when there is the slightest sign of this,

Use of Bunsen and Balance.

hold the tube almost horizontal, but with the hot part rather the higher : this prevents the condensed water running back on

the ‘hot glass. . , ,

The kind of balance usually employed in a laboratory is one

having a long index-finger depending from the arm with the point in front of a graduated scale. The swinging of the balance is shown by this index. When the weights placed in arc equal to the body being weighed, it vibrates to an equal distance each side of the zero mark on the scale. The body to be weighed is placed in the left-hand pan, and the weights in the right. When not in use the pans are supported ; by means of a handle they may be raised, and are then free to swing. The pans should always be dropped on their support when weights aic being added or removed. The weights used for chemical pin - poses are those of the metric system ; for their value, &c., the student should refer to the table given in Chapter 111. Never touch the more delicate weights with the fingers, but use the forceps found in the box with them ; great care must be taken that they are not soiled or otherwise injuied.

A laboratory note-book should always be kept, and an account entered in ink of every operation as performed. This applies with special force to weighing.

At the close of the laboratory lesson wash the glass apparatus, and wipe with a dry cloth any water, &c., from the retort stand, and other articles which might rust.

Chapter II. Modes Of Chemical Action And Separation

10. Heat, with other forces, acts over great distances.— Chemical attraction or affinity differs in one important particular from the other natural forces. These are capable of acting through distances which are, in many cases, enormous. Heat and light both reach us from the sun, and jn doing so travel over ninety millions of miles, but chemical

T cxt-Book of Inorganic Chemistry.

action can only take place where there is absolute contact between the substances participating in it.

Experiment 9. — Hold a red-hot iron bar some inches from a piece of phosphorus about the size of a pea. Observe that the heat travels over the intervening space and the phosphorus is inflamed, i.e. takes fire. (In this and similar experiments the phosphorus, or other inflammable material, should be placed on a piece of iron or other substance which will prevent the heat injuring the work-bench.)

Magnetism and electricity, in common with heat, act over distances ; a glass rod, when electrified, will cause the leaves of a delicate electroscope, which is some yards off, to diverge.

Experiment 10.— Electrify a piece of ebonite or a rod of shellac by rubbing with warm flannel ; hold it near some fragments of paper or other light objects ; they are attracted. If wished, a piece of glass rod or tube may be rubbed with silk, and used instead of the ebonite and flannel ; when the same effect is produced. Place a magnet near a suspended magnetic needle ; notice that the one end is attracted and the other repelled, though the two may be six or more inches apart.

11. Contact is required for Chemical Action.—

Experiments of a most careful character have been made, in order to measure, if possible, the distance through which chemical action can take place ; as a result it has been found that an interval unobservable to the naked eye is sufficient to prevent it.